1) Field of the Invention
The invention herein relates to bicycles, specifically a compound drive foldable bicycle.
2) Description of the Prior Art
Available in range differing structural arrangements, foldable bicycles essentially consist of a foldable locking device situated next to the crankarm mounting area that enables the unfolding and folding of the bicycle frame, thereby reducing the overall physical size of the bicycle to facilitate portability, shipping, and storage. As indicated in FIG. 1, the said foldable locking device 10 that provides for the unfolding and folding of the bicycle frame is generally disposed on the down tube 3 (or the top tube) in front of the crankarm mount 2 and functions as a pivot point on the down tube 3 (or the top tube) that enables the front wheel 4 to be unfolded forward into the state of utilization or folded backward into the state of non-utilization. That is, the physical size of the said bicycle is lessened by utilizing the down tube 3 (or the top tube) to fold the front wheel 4 rearward to the seatstays 5 and the chainstays 6, wherein the distance b between the said rear wheel axle 71 and the crankarm mount 2 remains totally unchanged.
Referring to FIG. 2, the structure of the said foldable locking device 10 is comprised of a female connector 101, a male connector 102, and a quick release handle 103, wherein the said female connector 101 and male connector 102 are respectively disposed at the anterior and the posterior sections 31 and 32 of the down tube 3 (or the top tube), with a locating pin 100 inserted to maintain them in a free swinging state; the said quick release handle 103 is installed to the male connector 102 by means of an adjustment screw 1031 that is capable of coupling the male and female connector 102 and 101. When the bicycle frame down tube 3 (or top tube) is unfolded, the said male and female connector 102 and 101 are brought into union and the said quick release handle 103 adjustment screw 1031 is horizontally guided into the locating notch 1011 at the exterior side of the female connector 101, thereby tensively nesting the handle 103 to effectively secure the coupling of the said male and female connector 102 and 101 and, furthermore, the anterior and the posterior sections 31 and 32 of the down tube 3 (or top tube) enable folding as required by the bicycle-use situation. After the quick release handle 103 is released, the adjustment screw 1031 is horizontally moved out of the female connector 101 locating notch 1011 to decouple the said male and female connector 102 and 101, following which the anterior and the posterior sections 31 and 32 of the down tube 3 (or the top tube) are folded by means of the locating pin 100 that functions as a pivot point, enabling the bicycle to be configured into the folded state as required.
Although utilizing the foldable locking device 10 as a pivot point to fold the front wheel 4 and down tube 3 towards the rear when the bicycle is not in use effectively reduces its overall physical size and, furthermore, virtually all currently available foldable bicycles have adopted such a method, the inventor of the invention herein realized following long-term usage that there are still several shortcomings that require further improvement, including:
(1) When folded, only the down tube 3 and the front wheel 4 are folded to the rear and the position of the rear wheel 7 at the other extremity of the bicycle frame remains unchanged and given that the distance b between the said rear wheel axle 71 and the crankarm mount 2 is typically of a definite proportion that cannot be too short (bicycle handling and comfort is adversely affected if the distance b is too long or too short), resulting in the drawback that the extent to which folding the down tube 3 and the front wheel 4 rearward for a decrease in overall physical size is limited by the said condition and cannot be further reduced.
(2) Since the coupling and decoupling of the said male and female connector 102 and 101 necessitates the turning of the quick release handle 103 at one side (the side opposite the locating pin 100) of the male and female connector and, furthermore, the down tube 3 (or the top tube) is typically folded towards the side of the chainring 8 (in the direction of the locating pin 100) to prevent hitting the chainring 8 when the bicycle frame down tube 3 (or top tube) is folded because the said quick release handle 103 is situated on the same side as the chainring 8, to facilitate turning it without hazardously impacting the chainring 8, virtually all said male and female connectors 102 and 101 (i.e., foldable locking devices) are usually installed at the anterior extent, upper extent, or lower extent (generally the upper or anterior extent ) of the chainring 8 and thus cannot be placed adjacent to the crankarm mount (the center of the chainring), the folded length and height of the said bicycle frame is subject to limitations and the smallest, most space-saving dimensions cannot be achieved and, at the same time, the design of the bicycle frame is also limited in that additional flexibility and variation is not possible.
(3) After the said male and female connector 102 and 101 are brought into union, since the said quick release handle 103 adjustment screw 1031 must be horizontally guided into the locating notch 1011, with the quick release handle 103 then nested under tension to achieve secure coupling, in addition to the relatively troublesome operation involved, notably because the said quick release handle 103 necessarily involves the application of considerable force to solidly couple the said male and female connector 102 and 101, the quick release handle 103 requires much strength to operate and, as such, has the shortcomings of exhaustive physical effort and attendant inconveniences.
(4) Since the said quick release handle 103 adjustment screw 1031 is horizontally guided into the locating notch 1011 formed in the female connector 101, if the tensive nesting of the quick release handle 103 is inadequate and the bicycle is ridden on roughly surfaced road, the said adjustment screw 1031 becomes dislodged and results in the dangerous separation of the anterior and the posterior sections 31 and 32 of the down tube 3 (or the top tube).
(5) Since the said adjustment screw 1031 of the said quick release handle 103 is horizontally articulated for engagement of the female connector 101 and disengagement of the female connector 101, the stance of the operator relative to the horizontally oriented quick release handle 103 is typically not within a natural angle of vision and conflicts with common working practices and, thus, does not comply with ergonomic principles of operation.
Based on the preceding section, the folding method of the said conventional foldable bicycle is obviously still unperfected and has numerous shortcomings that require further improvement.
The primary objective of the invention herein is to provide a compound drive foldable bicycle in which the bicycle in an unfolded state has a length between the outer edges of a front and a rear wheel that is divided into three sections such that the said rear wheel is swung up and down into the unfolded and folded state on a second drive shaft that serves as a pivot point and, furthermore, the rear wheel is postured at the lower extent of the chainring when it is folded, while the front wheel is horizontally swung for unfolding and folding via a foldable locking mechanism positioned on the down tube (or the top tube) and situated within the circumferential perimeter of the chainring such that the front wheel is postured at the lower extent of the saddle; as such, when the bicycle is in the folded state, it is of the smallest and most flexible physical dimensions to save space and reduce packaging material requirements, thereby facilitating storage, placement, and shipping.
Another objective of the invention herein is to provide a compound drive foldable bicycle, wherein the foldable locking mechanism that provides for the unfolding and folding of the front wheel by horizontal swinging is situated within the circumferential perimeter of the said chainring adjacent to its crankarm mounting area such that the folded length and height of the said bicycle frame is not only the smallest possible, but at the same time the design of the frame can be flexibly reshaped, adapted, and modified in a multiple variety of ways.
Yet another objective of the invention herein is to provide a compound drive foldable bicycle, wherein the said foldable locking mechanism has an adjustment screw that enables its unfolding and folding which is situated at the exact upper extent of a female connector and when rotated, a latch bolt accordingly ascends or descends to decouple and couple a male connector and the female connector; as such, the folding and unfolding of the said bicycle meets the requirements of ergonomic and natural operation, while the said unfolding and folding is reliable, solid, and stable, thereby precluding any possibility of hazardous slippage and separation.